1. Field of the Invention
The present invention relates to a process for making positive resist patterns having high sensitivity and high resolution toward high energy radiations such as electron beam, X rays, and deep ultraviolet rays, as well as dry etching resistance. More particularly, the invention relates to a process for making resist patterns which employ derivatives of polyacrylate esters having halogen atom and benzene ring for use as resist material.
2. Description of the Related Art
As an electron beam positive resist, well known is polymethyl methacrylate (hereinafter abbreviated as PMMA). Although PMMA is a high resolution, it is less sensitive and poor against the dry etching. For high sensitivity, polymers of esters of methacrylic and acrylic acid or derivative thereof with mono or polyfluoroalkanols are used as material of positive resists for making patterns against electron beam and so on (Japanese Laid-Open Patent application No. Sho 55-18638 and No. Sho 60-254041 etc.), but this material has been proved to have insufficient resistance against the dry etching, as it is the case with PMMA. On the other hand, polyhenylmethacrylates show improved resistance against dry etching, but are still as low in sensitivity as PMMA.
On the other hand, polymers of 2-pentafluorophenylhexafluoroisopropyl esters of (meth-)acrylic acid are known, for example, in U.S. Pat. No. 3,544,535 etc., but it is still unknown whether or not these polymers can be employed as material for making positive resist.
Recently, various polymers containing halogens such as fluorine are being investigated to develop the field of application with particular care in manifesting their characteristics. Attention is paid to their high sensitivity toward electron and X rays when used for material of the resist. However, their shortcoming resistance against dry etching a defect in their application to resist materials, while dry processes are being developed in today's micro-technology.
The present invention which has been pursued with a view mentioned above intends to find resist patterns having the improved resistance against dry etching.